Arc-flash protective apparatus

ABSTRACT

An arc-flash protective hood device. The protective hood is fitted with a passive ventilation device formed with facing plates, each plate having a plurality of slots therethrough, the slots in one plate being in offset registration with the slots in the other plate, thereby creating a semi-tortuous path for air flow through the ventilation device. The semi-tortuous path for air flow is so formed to prevent arc-flash energy from passing through the ventilation device. Alternatively, the ventilation device may be a single, integral element, or each plate may be made in two or more segments. The ventilation device may be mounted in an opening in a hood, and several ventilation devices may be mounted in several openings in the hood.

FIELD OF INVENTION

The present apparatus relates generally to the field of safety deviceswhich protect people from injury arising from electric-arc dischargesand more particularly to protective clothing, such as hoods and shrouds,which may be used together with safety helmets and face shields, forexample.

BACKGROUND OF THE INVENTION

Electrical arc-flash hazards are a known threat in some workplaces andmust be addressed to protect people who may be exposed to such dangerousconditions. Electric arcs or arc-flashes can result from short circuitsdeveloping from poor electrical grounding, failure of insulation, orworkers inadvertently contacting exposed electrical circuit elementswith objects such as tools. Electric arcs have extremely hightemperatures and near explosive power, and the energy they radiate canresult in serious or fatal injury. The energy of an arc-flash is veryintense and of very short duration. Flame resistant protective gear mustbe durable and able to withstand temperatures that may be as high as35,000° F. To protect workers from exposure to such arc-flash events, anumber of protective safety devices have been developed. In particular,face shields employing generally transparent windows comprised ofcompositions which have the ability for the user of the shield to seethe workspace and, at the same time, have the ability to substantiallyblock harmful radiation, are available. These devices are designed toprovide protection against the thermal, optical, and mechanical hazardsgenerated by arc-flash events. The protective compositions are referredto as energy absorbing materials and are classified by their calorieratings, that is, the level of energy for which they have been tested orcertified.

When situational conditions or regulations so require, protective hoodsare employed to protect the user's neck and upper shoulder area fromarc-flash damage. Lack of adequate ventilation is a typical consequenceof the fact that hoods must be tightly sealed to the user's helmet, orface shield, or both, and envelop at least part of the user's upperbody. Under typical working conditions, the upper body and head of theuser, being closely confined, can become uncomfortably hot and humid,and subject to build-up of CO2, due to inadequate provisions for air toeasily exhaust from the hood. It has been difficult to ventilate suchprotective clothing because of the potential arc-flash energy that couldpenetrate the clothing through openings intended to provide ventilation.Fan systems have been proposed with such hoods and have had somesuccess. They would likely be battery powered. Fans are likely to addunwanted bulk, weight, and noise.

SUMMARY OF EMBODIMENTS OF THE INVENTION

A problem addressed by embodiments of this invention is to provide userprotection in conditions where an arc-flash may occur, at the same timemaking the user more physically comfortable while working in such areaswith the gratifying knowledge that physical comfort has been measurablyincreased without degrading the level of protection afforded by theare-flash protective apparatus. Knowing that arc-flash protection ismaintained while physical comfort is increased enables a user to work ata high level of concentration to complete the job at hand quickly andefficiently.

An example of a purpose of the present concept is to maintainelectromagnetic energy and infrared energy protection while providingventilation for the user of protective face shields with arc-protectiveclothing, such as hoods or shrouds, jackets, bibs, or suits. The term“hood” will be used herein as a convenient means to refer to all sucharc-flash protective clothing.

A generally flat or planar ventilation device or assembly is mounted inan opening in the hood. The mounting is sufficiently sealed so that theprotective function of the hood is not compromised by installing one ormore such ventilation devices.

The ventilation device itself is generally comprised of two spacedfacing plates, an inner plate and an outer plate. Slots in the innervent plate are in offset registration with slots in the outer ventplate, thereby providing ventilation without degrading electromagneticenergy protection. The assembly of a paired inner vent plate with anouter vent plate may be mounted at any location, or more than onelocation, in a hood of the type that are typically employed in the fieldof protective clothing. The typical preferred location is at the back ofthe neck of the hood as worn by the user.

The term “offset registration” means that there is no directpass-through route through the ventilation assembly and that air, forexample, must move in a zig-zag, or semi-tortuous, path to pass from theinside to the outside, or vice versa. This offset registration resultsin electrical arc radiation being blocked and thereby allowingventilation of heated air from inside the hood while maintaining safetyof the user from electric are energy. The ventilation device is passive,meaning that all parts are in fixed relation to all other parts.

In an alternative embodiment, the ventilation device is formed of anouter plate having several parallel slots therethrough, and an innerbaffle plate connected to and spaced from the outer slotted plate. Thebaffle plate is not formed with slots and it performs essentially thesame function as the two facing plate embodiment with slots in offsetregistration.

While the device disclosed herein is particularly useful with arc-flashprotective gear, it is also useful for any work environment when a hoodis worn by the user for protection and heat builds up inside the hood.

BRIEF DESCRIPTION OF THE DRAWING

The purposes, features, and advantages of the disclosed structure willbe more readily perceived from the following detailed description, whenread in conjunction with the accompanying drawing, wherein:

FIG. 1 is a perspective view of a protective hood with a face shield ofthe prior art;

FIG. 2 is a perspective view of a shroud connected to a safety helmetand having a face shield of the prior art;

FIG. 3 is a somewhat schematic view of the back of a hood as it mightappear with a ventilation device in accordance with embodiments of theinvention mounted therein;

FIG. 3A is a partial sectional view of the ventilation device and hoodfabric of FIG. 3;

FIG. 4 is a plan view of an embodiment of a ventilation device of thisinvention;

FIG. 4A is a partial sectional view taken along cutting plane 4A-4A ofFIG. 1;

FIG. 5 is an exploded perspective view of the ventilation device of FIG.4 from one side;

FIG. 6 is an exploded perspective view of the ventilation device of FIG.4 from the opposite side;

FIG. 7 is a plan view, similar to FIG. 4, of an alternative embodimentof a ventilation device of this invention;

FIG. 8 is an exploded perspective view of the ventilation device of FIG.7;

FIGS. 9A-9E are plan views of embodiments of the ventilation devicesimilar to FIGS. 4-6 and having alternative shapes;

FIG. 10 is a partial perspective view of a segment of the back of a hoodwith a group of four ventilation devices of FIG. 4 mounted therein;

FIGS. 11A-11E are partial perspective views similar to FIG. 10 showinggroupings of the ventilation devices of FIG. 9 mounted in the fabric ofa hood;

FIGS. 12A-12C are schematic partial sectional views of the type of FIG.3A showing alternative mountings of embodiments of ventilation devicesof the prior figures as they can be secured in openings in a hoodfabric; and

FIGS. 121D-12E show alternative embodiments of the ventilation devicesof the prior figures as mounted in different ways in openings in a hoodfabric.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For reference purposes, FIG. 1 shows a typical hood 71 and protectiveface shield, and FIG. 2 shows a typical shroud 72 connected to a safetyhelmet and having a protective face shield, either of which may be usedtogether with the ventilation device described herein. The onlysignificant difference between the shroud of FIG. 2 is that it isattached to a helmet, whereas the hood of FIG. 1 is not attached to ahelmet and fits over the user's head. Of course, a helmet shouldnormally be worn by the user of the hood apparatus. Protective faceshields are typically made of polycarbonate with additives of organicdyes or nanoparticles, or a combination of both. Suitable fabrics fromwhich protective hoods may be made are available from commercialsources. Typical acceptable fabrics include WESTEX, a registeredtrademark of Milliken & Company, and PROTERA and NOMEX MHP, registeredtrademarks of E.I. du Pont de Nemours and Company.

Given the situation when a worker is wearing a hood and protective faceshield, as in FIGS. 1 and 2, plus a helmet, and is working in apotentially dangerous arc-energy area, heat may quickly build up withinthe hood. The preferred location for ventilation device 11 in hood 71,72 is at the back of the neck as shown in FIG. 3, where the hood fabricwould normally not be in contact with the user's skin and air can flowrelatively freely. In this position the heated and possibly otherwisefouled air can escape, clear of any work area. Any location from theback of the user's head to the shoulders or below could provide thedesired ventilation function.

To prepare the hood to receive ventilation device 11, a rectangularopening 76 is made in the hood in the area that would be at the back ofthe user's neck or in that general vicinity, and the unitary orassembled ventilation device 11 (described in detail herein) is securedin the opening by suitable means. While it could be secured by anappropriate adhesive, for example, the preferred method is to stitch thedevice to the hood with appropriate fire-retardant thread material 75 ingroove 45 (see FIG. 1). Stitches of thread 75 can be seen in FIG. 3.Examples of materials from which thread 75 can be made includefiberglass, and KEVLAR and NOMEX, both registered trademarks of E.I. duPont de Nemours and Company for synthetic fibers and fabrics made fromthose fibers.

As can be seen in FIG. 3A, opening 76 in hood 71 is peripherally smallerthan is ventilation device 11, enabling stitches 75 to positively securethe ventilation device in the opening.

With reference now to FIGS. 4-6, ventilation device 11 is preferablycomprised of front, or first, plate 12 mounted to back, or second, plate13. The terms “front” plate and “back” plate, or “first plate” and“second plate,” are used for convenience only and are not intended todesignate a particular one of those plates to be outside or inside withrespect to the clothing items to which the ventilation device isintended to be mounted. Either, or both plates, could be made of morethan one plate or as a unitary plate, as is deemed practical andappropriate for the purpose for which it is intended to be used. Asfurther alternatives, the entire ventilation device 11 could be formedas a unitary product, which could be injection molded, 3-D printed, ormade by some other process.

For purposes of this description, front and back plates 12 and 13 anddevice 11 will be discussed as having the parameters set forth below, nomatter how the device is formed or assembled.

Plate 12 is formed with a plurality of parallel slots 14 therethrough.Plate 13 is formed with a plurality of parallel slots 15 therethrough.As shown, there are ten slots in plate 12 and nine slots in plate 13.There is no requirement that the number of slots be any particularnumber, only that they be offset with respect to each other when theplates are assembled in face-to-face relationship. Also, the number ofslots through plate 12 may be the same as the number of slots in plate13. That structural requirement will be discussed further below.

Plate 12 is shown formed with registration pins 16 near the periphery ofeach corner. Plate 13 is formed with similarly positioned matching holes17. These may be blind holes or through holes. Holes 17 are configuredto match with pins 16 so that plates 12 and 13 can be secured togetherin fixed registration relationship. It is preferred that plates 12 and13 be secured together to form a unitary device, as shown in FIG. 4.

The side of plate 12 facing plate 13 is formed with stand-offs 21 whichcontact the inside surface of plate 13 and maintain air flow spaces 31between the plates. As shown in FIG. 5, rim 22 and stand-offs 21 are allof the same thickness. As an alternative way of saying it, the rim andthe stand-offs are in the same plane on the side of plate 12 facingplate 13. The remaining portion of the inside surface of plate 12,including lands 23, is depressed, or thinner than are rim 22 andstand-offs 21, thereby forming lateral air flow spaces 31.

As can be seen in FIG. 4, when holes 17 in plate 13 are in registrationwith pins 16 in plate 12 and the two plates are mounted together, slots14 and 15 are in offset registration, as previously stated. Air can flowin through slots 14, pass laterally in spaces 31 between the plates fora short distance between the inside surface of plate 13 and lands 23,and flow out through slots 15 in plate 13 in a semi-tortuous manner. Ofcourse, flow could just as well be in the opposite direction. Becauseplate 13 is planar and rim 22 and stand-offs 21 are co-planar, air isgenerally confined to spaces 31 for lateral movement. However, it is notnecessary that plates 12 and 13 be sealed together, but they wouldgenerally be secured together and the inside surface of plate 13 wouldbe in contacting relation with rim 22 and stand-offs 21.

The spaces 31 between the inside surface of plate 13 and lands 23 ofplate 12, in relation to the width of the slots, should be just enoughto prevent any direct flow of arc energy through device 11. One test toensure that arc energy cannot pass directly through device 11 is to viewthe device normal to the slots and at a 45° angle from above the device.If there is no direct visibility through device 11 from that position,there would be no penetration of arc-flash energy therethrough. Statedanother way, spaces 31 needs to be only sufficiently separated from theinside surface plate 13 to permit lateral air flow between plates 12 and13 within the spaces 31.

Ventilation device 11 may be formed of known arc-flash or arc-energyresistant or absorbing material, such as rubber or a thermoplastic,having the same calorie rating as would a face protective shield orwindow and the hood used with the window. There may be severalformulations of the constituents of which plates 12 and 13 are formed.Device 11 must be electrically non-conductive. Any materials which meetthe protective, energy absorbing requirements of the hood fabric and theprotective window, would normally be acceptable for these ventilationdevice plates.

Ventilation device 11 may be made from a thermoplastic elastomers orthermoplastic vulcanizate such as SANTOPRENE, a registered trademark ofExxon Mobil Corporation. Alternative materials from which device 11 canbe formed include EPDM rubber, silicone rubber, or neoprene rubber.There may be other high temperature resistant materials that areacceptable. As a further example, carbon black may be added toSANTOPRENE to result in an arc-energy blocking device. Other materialsthat are tuned to the electromagnetic spectrum of an arc-flash (200-3000nm as an example), include organic dyes, nanoclays, and nanoparticles.

The structure of device 11 ensures that there is no direct, unimpededfluid flow route from one side to the other, so the user is protectedfrom potential arc-flash injury. At the same time, ventilation air canflow through device 11 as previously described, providing much neededventilation for the user when wearing a ventilation device equippedhood.

Plate 12 is formed with narrow peripheral groove 45 (FIGS. 4, 6, and 7)in rim 22, just inside edge 46. This is used in securing ventilationdevice 11 to clothing, as will be discussed below. This is shown clearlyin the cross-sectional view of FIG. 4A.

An alternative embodiment of device 11 is shown in FIGS. 7 and 8. Device11 may be relatively rigid. When the ventilation device is made ofmaterials which are somewhat flexible, such as rubber, it has been foundthat bridges 41 help maintain stability of lands 23 and, consequently,of slots 14 with respect to each other in plate 12. Similarly, bridges42 span slots 43 in plate 13 for the same purpose.

FIGS. 9A-E shows examples of possible shapes of ventilation device 11 inaddition to the rectangular shape of FIG. 4. Each would include the samecharacteristics as the devices of FIGS. 4-8 so those will not bedescribed in detail.

In FIG. 9A, ventilation device 61 is square, device 62 in FIG. 9B ishexagonal, device 63 in FIG. 9C is circular, device 64 in FIG. 9D isoval, and device 65 in FIG. 9E is octagonal. There may well be otherpossible or suitable shapes and those shown in the drawing are examplesonly.

Some alternative hood/ventilation device arrangements are shown in FIGS.10 and 11A-E. Hood segments 71 are employed in each figure withdifferent ventilation device installations. For explanatory purposes, inFIG. 10 each hood segment is fitted with four ventilation devices.Depending upon the requirements of the purchaser, the number ofventilation devices could be as few as one to as many as size permitsand requirements dictate.

In FIG. 10 there are four rectangular ventilation devices 11 arranged asshown. In this case the slots are oriented horizontally, but they couldbe oriented vertically as well.

Ventilation devices 61 are mounted to hood 71 in a square group ofsquare ventilation devices in FIG. 11A. A group of four hexagonalventilation devices 62 are shown in FIG. 11B, a group of four circulardevices 63 are mounted in hood 71 in FIG. 11C, four oval devices 64 areshown in FIG. 11D, and four octagonal devices 65 are shown in FIG. 11E.

The manner of attachment, and some variations in the schematic partialcross-sectional representations of ventilation devices as they may bemounted to hood 71 are shown in FIGS. 12A-E.

FIG. 12A represents the mounting arrangement of FIG. 3, where device 11is mounted on the inside of the fabric of hood 71. Alternatively, device11 can be mounted over opening 76 on the outside of the hood fabric, asshown in FIG. 12B.

An alternative is shown in FIG. 12C, where device 11 is formed with aperipheral groove or slot 81 at the intersection of plates 12 and 13 sothat the edges of opening 76 in the hood fabric are within that slot andthe stitches are applied in the same way as before, through the hoodfabric and through plates 12 and 13 in groove 45.

As another alternative mounting method, hood 71 can be two-ply anddevice 11 may be sandwiched between the hood fabric sheets, somewhat asa combination of FIGS. 12A and 12B.

In FIGS. 12D and 12E the ventilation device 18 has the usual plate 12and a modified inside element 82 instead of flat plate 13. The samecriteria apply as before, that is, that there is no direct path throughthe slots in plate 12 that can get past element 82 so any arc-flashenergy cannot get through hood 71. Any energy that enters through theslots in plate 12 are blocked by element 82. With this configurationelement 82 does not have any slots at all because air is ventilatedthrough the space between plate 12 and element 82. Any arc-flash energythat impinges upon front plate 12 is partially blocked and absorbed byplate 12, and any such energy that passes through slots in plate 12 isabsorbed and deflected by baffle plate 82. Even though there are noslots in plate 82, the flow through plate 12 to plate 82 is still in asemi-tortuous path.

Plate 12 in FIG. 12D is mounted in opening 76 in hood 71 in the samematter as shown in FIG. 12A. Plates 12 and 82 in FIG. 12E are mounted tohood 71 as shown in FIG. 12B at the top and as shown in FIG. 12C at thebottom where edge 76 of the hood opening is in a groove at theintersection of the two plates.

The alternative configurations and mounting arrangements of FIG. 12 areprovided to show that there may be many ways that the ventilation devicemay be mounted in an opening 78 in the fabric of hood 71, and these aremerely examples to suggest that there may be many more.

While the ventilation device described here would likely provideadequate ventilation under many environments, it could also be used inconjunction with a fan system for enhanced ventilation.

What is claimed is:
 1. A device for use with a safety face shieldassembly, the device comprising: a hood configured to cover at least thehead of a wearer and incorporating the safety face shield, the hood andsafety face shield being formed of materials that protect the wearerfrom arc-flashes, said hood having an opening in at least one location;a passive ventilation device mounted in said opening, said passiveventilation device having a periphery, said hood being secured to theperiphery of said passive ventilation device, said passive ventilationdevice comprising: a relatively rigid first plate having a firstplurality of slots therethrough; and a relatively rigid second platehaving a second plurality of slots therethrough; said first and secondplates being arranged in face-to-face relationship with said slots insaid first and second plates being in offset registration so that thereis no direct fluid flow route through the slots in said front and backplates, thereby providing a semi-tortuous path for ventilation betweeninternal and external sides of said hood, said ventilation device beingformed of materials that block arc-flashes, the semi-tortuous paththereby protecting the wearer from an external arc-flash.
 2. The passiveventilation device recited in claim 1, wherein said first plurality ofslots in said first plate differs in number from said second pluralityof slots in said second plate.
 3. The passive ventilation device recitedin claim 1, wherein said first plurality of slots in said first plate isequal in number to said second plurality of slots in said second plate.4. The passive ventilation device recited in claim 1, wherein said firstplate is formed with a peripheral rim that is thicker than a centralportion of said first plate which central portion faces said secondplate, thereby permitting air flow in a semi-tortuous path from theslots in one of said first and second plates to and through the slots inthe other of said first and second plates.
 5. The passive ventilationdevice recited in claim 4, wherein said central portion of said firstplate is formed with a plurality of stand-offs which are in the plane ofsaid peripheral rim.
 6. The passive ventilation device recited in claim1, wherein said first plurality of slots defines a first plurality oflands therebetween, and said second plurality of slots defines a secondplurality of lands therebetween.
 7. The passive ventilation devicerecited in claim 5, wherein said first plurality of slots defines afirst plurality of lands therebetween, and said second plurality ofslots defines a second plurality of lands therebetween and wherein saidplurality of stand-offs are formed on said first plurality of lands tomaintain spacing between the facing surfaces of said first and secondplates.
 8. The passive ventilation device recited in claim 6, andfurther comprising a first plurality of bridges in said first pluralityof slots between each two of said lands defining each said slot, saidfirst plurality of bridges connecting adjacent lands of said firstplurality of lands.
 9. The passive ventilation device recited in claim6, and further comprising a second plurality of bridges in said secondplurality of slots between each two of said lands defining each saidslot, said second plurality of bridges connecting adjacent lands of saidsecond plurality of lands.
 10. The passive ventilation device recited inclaim 1, wherein said first plate is formed with a peripheral groove inthe surface facing away from said second plate.
 11. The device recitedin claim 10, wherein said passive ventilation device is mounted in saidopening by stitches through said peripheral groove in said first plate,through said second plate, and through the hood material.
 12. A passiveventilation device for use in a hood made of arc-flash protectivematerial and having at least one opening through the protectivematerial, said ventilation device having a periphery adapted to besecured in the opening in said hood, said passive ventilation devicecomprising: a first plate having a first plurality of slotstherethrough; and a second plate having a second plurality of slotstherethrough; said first and second plates being arranged inface-to-face relationship with said slots in said first and secondplates being in offset registration so that there is no direct fluidflow route through the slots in said first and second plates, therebyproviding a semi-tortuous path for ventilation between internal andexternal sides of said hood, said ventilation device being formed ofmaterials that block arc-flashes, the semi-tortuous path therebyprotecting the wearer from an external arc-flash.
 13. The passiveventilation device recited in claim 12, wherein said first plurality ofslots in said first plate differs in number from said second pluralityof slots in said second plate.
 14. The passive ventilation devicerecited in claim 12, wherein said first plurality of slots in said firstplate is equal in number to said second plurality of slots in saidsecond plate.
 15. The passive ventilation device recited in claim 12,wherein said first plate is formed with a peripheral rim that is thickerthan a central portion of said first plate which central portion facessaid second plate, thereby permitting air flow in a semi-tortuous pathfrom the slots in one of said first and second plates to and through theslots in the other of said first and second plates.
 16. The passiveventilation device recited in claim 15, wherein said central portion ofsaid first plate is formed with a plurality of stand-offs which aresubstantially equal in thickness to said peripheral rim.
 17. The passiveventilation device recited in claim 12, wherein said first plate iscomprised of at least two coplanar segments.
 18. The passive ventilationdevice recited in claim 12, wherein said second plate is comprised of atleast two coplanar segments.
 19. The passive ventilation device recitedin claim 12, wherein said first plate is formed with a peripheral groovein the surface facing away from said second plate.
 20. The passiveventilation device recited in claim 19, wherein said ventilation deviceis securable in said opening in said hood by stitches through saidperipheral groove in said first plate, through said second plate, andthrough the hood protective material.
 21. A device for use with a safetyface shield assembly, the device comprising: a hood configured to coverat least the head of a wearer and incorporating the safety face shield,the hood and safety face shield being formed of materials that protectthe wearer from arc-flashes, said hood having an opening in at least onelocation; a passive ventilation device mounted in said opening, saidpassive ventilation device having a periphery, said hood being securedto the periphery of said passive ventilation device, said passiveventilation device comprising: a first plate having a first plurality ofslots therethrough; and a baffle plate mounted to and at least partiallyspaced from said first plate; said first and baffle plates beingarranged in face-to-face relationship so that there is no direct fluidflow route through the slots in said first plate and past said baffleplate, thereby providing a semi-tortuous path for ventilation betweeninternal and external sides of said hood, said ventilation device beingformed of materials that block arc-flashes, the semi-tortuous paththereby protecting the wearer from an arc-flash.
 22. The device recitedin claim 21, wherein said first plate is formed with an inside surfaceand an outside surface and a peripheral groove in one said surface. 23.The device recited in claim 22, wherein said passive ventilation deviceis mounted in said opening by stitches through said peripheral groove insaid front plate and through said hood protective material.
 24. Apassive ventilation device for use in a hood made of arc-flashprotective material and having at least one opening through theprotective material, said passive ventilation device having a peripheryadapted to be secured in the opening in said hood, said passiveventilation device comprising: a first plate having a first plurality ofslots therethrough; and a baffle plate mounted to and at least partiallyspaced from said first plate; said first and baffle plates beingarranged in face-to-face relationship so that there is no direct fluidflow route through the slots in said first plate and past said baffleplate, thereby providing a semi-tortuous path for ventilation betweeninternal and external sides of said hood, said passive ventilationdevice being formed of materials that block arc-flashes, thesemi-tortuous path thereby protecting the wearer from an arc-flash. 25.The passive ventilation device recited in claim 24, wherein said firstplate is formed with an inside surface and an outside surface and aperipheral groove in one said surface.
 26. The passive ventilationdevice recited in claim 25, wherein said ventilation device is securablein said opening in said hood by stitches through said peripheral groovein said front plate and through said hood protective material.